Kinetic studies are being pursued in conjunction with immunological approaches to identify cell surface materials contributing to embryonic cell adhesion. Embryonic chick neural retina cells are being tested using an aggregate collection assay. An antiserum directed against neural retina membranes specifically inhibits collection of cells to aggregates. Immunological and biochemical approaches are being persued to identify the antigen(s) involved. BIBLIOGRAPHIC REFERENCES: McClay, D.R. (1976) Kinetic approaches to embryonic cell adhesion. In: "Tests of Teratogenicity in vitro." North Holland, Amsterdam. pp. 187-200. McClay, D.R., A.F. Chambers and R. Warren (1977) Specificity of cell-cell interactions in sea urchin embryos. Appearance of new cell surface determinants at gastrulation. Develop. Biol. In press.